Method of granulating asphaltic materials



United States Patent Ofitice 3,235,483 Patented Feb. 15, 1966 3,235,483 METHOD F GRANULATING ASPHALTHC MATERIALS Frederic C. McCoy, Beacon, and Edwin C. Knowles,

Poughlreepsie, N.Y., assignors to Texaco Inc., New

York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 24, 1963, Ser. No. 275,226

3 Claims. (Cl. 208-39) This invention relates to a method of finely-dividing asphaltic material.

This application is a continuation-in-part of copending application Serial No. 182,385, filed March 26, 1962.

Asphalts occur naturally or in certain materials such as petroleum crude oils. For example, they may be obtained from petroleum crude oils as a residuum on vacuum distillation or on solvent deasphalting of the crude. The resulting asphalt obtained from the crude may be further treated as by air blowing to improve the plastic and elastic properties of the asphalt. Asphalts are generally regarded as complex systems consisting essentially of highly carbonaceous asphaltenes colloidally dispersed in a hydrocarbon oily medium, and hydrocarbon resins which act as stabilizers.

Asphalts exhibit definite plastic or flow characteristics, the most important of which are penetration and softening point measured in accordance with certain empirical tests as established by the American Society for Testing Material (ASTM). The penetration (ASTMD5D2) is determined by measuring the distance in tenths of a millimeter that a standard needle penetrates into the asphalt under controlled conditions with a definite load, e.g., 100 grams at 77 F. for a five-second period. The softening point (ASTM D36-26) is determined by filling a brass ring /8 inch in diameter with asphalt, placing a inch steel ball on the asphalt, and raising the temperature uniformly until the ball drops through. Thus, the consistency for asphalts measured in terms of ASTM penetration at 77 F. with a load of 100 grams for a 5- second period may range from 03 for a very hard asphalt to about 300 for a very soft asphalt, and the softening point (ring and ball) for asphalts may range from about 100 F. to 350 F. or higher, the higher softening points generally indicating harder asphalts.

Certain uses require the asphalt to be in a finelydivided state, i.e., in a powder or grain form. 'In the past finely-divided asphalt at room temperature normally could only be derived from relatively hard grade asphalt, that is, one having an ASTM penetration at 77 F. of 5 or less and an ASTM ring and ball softening point above 250 F. The brittle (hard) asphalts were often granulated by dry mechanical attrition or wet grinding methods. However, even very hard asphalts were sometimes difficult to pulverize by conventional techniques. For example, a case was reported in the literature where an asphalt of a 310 F. ring and ball softening point agglomerated during wet grinding in a ball mill.

Copending application Serial No. 182,385 describes a wet method by which free flowing finely-divided asphaltic material can be prepared utilizing a higher penetration and lower softening point asphalt than heretofore considered possible. The parent application calls for a wet granulation method which requires melting asphaltic material and introducing the molten material into an anticoalescing liquid in which the asphaltic material is relatively insoluble, such as water. The anti-coalescing liquid is maintained at a temperature below that of the softening point of the asphaltic material whereby the asphaltic material separates into a finely-divided material. To the recovered finely-divided material there is optionally added agents, such as silica, calcium silicate and talc. Although this method permits use of softer asphalts than many prior art methods of dry comminution, it does have the disadvantage of complexing the granulating process in that it requires the use and handling of anti-coalescing liquid and the separation of the finely-divided asphaltic materials from said coalescing liquid. Further, it requires putting the asphaltic material in the molten state.

We have discovered, and this constitutes our invention, a method which combines the simplicity of the prior art dry mechanical attrition with the ability to employ asphaltic materials as soft as in the wet method of the parent application. In other words, we have discovered a method of producing finely-divided, agglomeration-resistant particles which combines the economy and simplicity of the ry attrition method with the flexibility of being able to use a broader range of asphalts including those of a softness which heretofore could not be successfully powdered by dry mechanical attrition at normal temperature. Further, our method promotes the formation of finelydivided particles of relatively soft asphaltic material which are resistant to agglomeration even after long periods of storage.

Specifically, we have discovered that free flowing finelydivided asphaltic material can be produced even from relatively coarse, low softening point and high penetration asphaltic material by subjecting said material to dry mechanical attrition in the presence of carbon black. It has been found that when carbon black of a surface area of at least about 100 sq. meters/gram is present during attrition, asphalts having a ring and ball as low as about 160 F. and a penetration at 77 F. (5 seconds-100 grams) as high as about 30 can be easily granulated at room temperatures without the agglomeration of the asphaltic particles even after storage for a considerable period of time.

We have further discovered that the contemplated carbon black unexpectedly in some manner not fully understood interacts with the asphaltic material during attrition in a manner to promote the mechanical breakup of the asphaltic material as well as preventing agglomeration after particlization. When materials such as talc and calcium silicate are substituted for carbon black in the dry attrition process, the particle fineness and free-flowing condition of the asphaltic material is substantially less for a given set of conditions, even though substantially greater quantities of these substitute agents are employed.

In greater detail, asphalt to be finely-divided, advantageously of a ring and ball softening point of between about 160 and 350 F. and penetration at 77 F. (5 seconds-100 grams) of between about 0 and 30, is added to a dry mechanical attrition device at room temperature, e.g., between about 60 and F. together with between about 1 and 25% carbon black based on the weight of the asphalt, said carbon black having a surface area of at least about sq. meters/ gram. The attrition apparatus is then operated until the desired asphalt fineness is attained.

Another embodiment of the invention is to operate the above-described dry attrition process at reduced temperatures, e.g., as low as about 32 F. The lower the attrition temperature, the lower the minimum softening point and the higher maximum penetration for the asphaltic material to be finely divided. For example, at attrition temperatures of about 32 F., asphaltic material of a ring and ball softening point as low as about F. and a penetration as high as about 60 can be employed.

Although reduced temperatures in the granulating apparatus can be accomplished by conventional refrigeration such as through the use of cooling coils one particularly suitable method is incorporating powdered Dry Ice, desirably between about 5 and 50 wt. percent based on the asphalt, in the mixture of asphaltic material and carbon black during or just before attrition.

It was found that for a given set of conditions the cooling aided in producing smaller particle sizes and helped permit the granulation of much softer asphaltic material.

One essential feature of the invention is the use of carbon black having a surface area of at least about 100 sq. meters/ gram. The effectiveness of the carbon black in promoting a more finely-divided, agglomeration-resistant product has been discovered to be partially a function of the surface area of the carbon black. For example, it has been found when comminuting asphalts (e.g., R. & B. of 190 F.) in the presence of carbon black of a surface area of about 30 sq. meters/ gram in amounts of up to 15 wt. percent based on the asphalt, relatively coarse, non-fiowable agglomerating asphalt particles are produced. On the other hand, carbon black having a surface area of 1,000 sq. meters/gram in amounts of about 5.0 wt. percent produce a substantially finer asphalt product in which the individual particles are free-flowing and non-tacky even after long periods of storage.

Specific examples of asphaltic substances which can be employed for comminution are the natural asphalts, such as gilsonite and wurtzilite, asphalts derived from airblowing petroleum residuums, and asphaltic residuums produced upon distillation and solvent deasphalting of petroleum. A specific suitable hard asphalt has a ring and ball softening point of between about 275-300" F. and is derived from an air-blowing mixture of petroleum residuum and furfural extracts from a sulfuric acid treated petroleum residuum having a penetration of between about 50 and 125 (77 F., 100 grs., 5 secs.) and a minimum flash point of 450 F. This asphalt when finely divided is particularly suited as a drilling mud additive in oil and gas well production. A specific soft asphalt has a ring and ball softening point of 155 F. and a penetration of 49 (77 F., 100 grs., 5 secs).

The dry granulation method of the invention can employ any of the well known attrition techniques, such as crushing, grinding, and cutting. The type of apparatus which is particularly suitable for our method on a commercial scale are those devices which accomplish granulation by shearing and cutting such as the Ball and I ewell rotary cutter, the Sprout-Waldron rotary knife cutter, and the Abbe rotary cutter. These devices are described on page 1916 of the Chemical Engineers Handbook, sec nd edition (textbook edition), McGraW-Hill Book Company, Inc., New York, 1941.

The particle size of the initial asphaltic materials introduced into the granulating apparatus will be determined by the character of the granulating apparatus as well as the size of the finely-divided particles desired. One method of putting the asphaltic material into suitable size for attrition can be accomplished by heating the asphaltic raw material until plastic and extruding the plastic asphalt through dies of suitable diameter, e.g., to /2 inch and then cutting the extruded asphalt into suitable lengths, e.g., A to /2 inch. Further the asphaltic raW material may be coated with an anti-caking agent such as calcium silicate or talc. This precoating facilitates the loading and operation of the granulation apparatus since it aids in retarding the sticking together of the individual chunks of pregranulated asphaltic raw material.

The following examples further illustrate the invention but are not to be taken as a limitation thereof:

Example I This example illustrates the function of the carbon black and its advantage over related materials.

To a Waring Blendor there was added carbon black of 600 sq. meters/ gram surface area and an average particle size of 9 millimicrons. In addition, there was added asphalt having an ASTM ring and ball softening point of 191 F. and penetration at 77 F. (100 grams, seconds) of 31 in the form of /2 x A x A inch pellets. The Waring Blendor was then operated at 10,000 rpm. for a period of 3 minutes at about 80 F., followed by a sieve analysis (U.S. Standard) of the resultant granulated product. The foregoing procedure was repeated utilizing as a substitute for carbon black, talc having a surface area of 93 sq. meters/ gram and calcium silicate of 2.1 micron average particle size. One run was made using asphalt only. The test data results are reported below in Table I:

1 Trace.

Composition A product particles were very free-flowing and did not agglomerate after storage for 7 months.

Composition B product particles were not free-flowing and are highly charged and difficult to bottle. On standing, they tended to stick together.

Composition C product particles were less free-flowing and had a greater tendency to stick together than Composition A product particles.

Composition D product particles immediately agglomerated and could not pass a No. 10 sieve.

As can be seen from the above, Composition D which was asphalt alone upon granulation produced coarse, adherent nonfiowing particles which were all retained on a No. 10 sieve. Composition B which contained in addition to the asphalt 10 wt. percent talc produces particles which only 60% pass a No. 40 sieve and which tend to stick together upon storage. Composition C demonstrates that the 10 wt. percent of calcium silicate in asphalt produces asphaltic particles in which 86% pass a No. 40 sieve and particles which have some sticking tendencies. However, in Composition A containing only 5 wt. percent carbon black 97% of said composition passed the No. 40 sieve and the individual particles therein were completely free flowing even after standing at room temperature for an extended period.

Example II This example illustrates the criticality of maintaining the surface area of the carbon black above about 100 sq. meters/ gram.

The procedure of Example I was repeated except the raw asphalt pellets employed were coated with powdered calcium silicate in an amount of 0.5 wt. percent and the variable was carbon blacks of a different surface area. The data and results are reported below in Table II.

TABLE II E F G H I J Composition, Raw Material:

Asphalt, grs 20 20 20 20 20 20 Carbon Black, grs 1 1 2 2 1 2 Properties of Carbon Black:

Surface Area, sq. meters] gram 31 154 470 600 1, 000 Particle Size average, millimieron 83 28 20 11 9 7 Sieve Analysis of Asphalt Product (U.S. Standard):

Retained on No. 10, wt.

percent 1.0 0 0 0 0 0 Retained on No. 20, wt.

percent 2.5 2. 3 2. 3 2. 3 0 0 Retained 011 N0 40, wt

percent 24.7 13.9 6.8 4.5 0 O Passing No. 40, wt. percent. 71. 8 83.8 90. 9 93. 2 100 Composition E product flowed slu-ggishly when fresh and became tacky and non-fiowable in a few hours.

Composition F product flowed when fresh but became adherent and non-flowable in a few hours.

Composition G product was free-flowing after three days.

Composition H, I and I products were free-flowing after three days with no indication of a tendency for adhering.

As can be seen from the above table, it was not until carbon black having a surface area of about 100' sq. meters/gram was employed that the powdered asphalt product was free-flowing with little or no tendency to become coherent. Further, it can be seen that the fineness of the asphaltic product increases as the surface area of the carbon :black increases.

Example 111 This example illustrates the function of carbon black in promoting a fine free-flowing product with soft asphalts at reduced temperatures.

To a Waring Blendor there was added 2 grams of carbon black having a surface area of 600 sq. meters/ gram and a particle size of 9 millimicrons. There was also added asphalt having an ASTM ring and ball softening point of 142 and penetration at 77 F. (100 grams, 5 seconds) of 56 in the form of /2 x A; x A inch pellets. The Waring Blendor was then operated at 10,000 rpm. for a period of 3 minutes at 32 F. and a sieve analysis found that the product passed in 100% quantities a No. 40 US. Standard sieve.

Example IV The procedure of Example III was repeated except attrition was conducted at 80 F. utilizing asphalt having a ring and ball softening point of 160 and a penetration (77 F., 100 grs., 5 secs.) of 16. The final ground product passed in 100% quantities a No. 40* US. Standard sieve.

We claim:

1. A method of producing finely-divided asphalt comprising comminuting in a dry state at a temperature between about 32 and 90 F. a mixture of asphalt and carbon black, said asphalt having a ring and ball softening point t of between about 140 and 350 F. and an ASTM penetration at 77 F. (100 grams, 5 sec.) between about 0 and 60, said carbon black being present in said mixture in an amount :between about 1 and 25 weight percent based on said asphalt and said carbon black having a surface area greater than about 100 sq. meters/ gram.

2. A method of producing finely-divided asphalt comprising comminuting in a dry state at a temperature between about and F. a mixture of asphalt and carbon black, said asphalt having a ring and ball softening point of between about 160 and 350 F. and an ASTM penetration at 77 F. grams, 5 seconds) of between 0 and 30, said carbon black being present in said mixture in an amount between about 1 and 25 weight percent based on said asphalt, said carbon black having a surface area greater than about 100 sq. meters/gram and said comminuting accomplished by a cutting action.

3. A method in accordance with claim 1 wherein said temperature is maintained by adding Dry Ice to the initial asphalt carbon black mixture.

References Cited by the Examiner UNITED STATES PATENTS 441,951 12/1890 Goetz 241-23 727,507 5/1903 Warren 106281 738,966 9/1903 Warren 106281 2,347,464 4/ 1944 Cuno 241-23 OTHER REFERENCES Perry, Chemical Engineers Handbook, Third Ed. (1950), pp. 1156 and 1157, McGraw-Hill Book Co., Inc., New York.

DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner. 

1. A METHOD OF PRODUCING FINELY-DIVIDED ASPHALT COMPRISING COMMINUTING IN A DRY STATE AT A TEMPERATURE BETWEEN ABOUT 32 AND 90*F. A MIXTURE OF ASPHALT AND CARBON BLACK, SAID ASPHALT HAVING A RING AND BALL SOFTENING POINT OF BETWEEN ABOUT 140 AND 350*F. AND AN ASTM PENETRATION AT 77*F. (100 GRAMS, 5 SEC.) BETWEEN ABOUT 0 AND 60, SAID CARBON BLACK BEING PRESENT IN SAID MIXTURE IN AN AMOUNT BETWEEN ABOUT 1 TO 25 WEIGHT PERCENT BASED ON SAID ASPHALT AND SAID CARBON BLACK HAVING A SURFACE AREA GREATER THAN ABOUT 100 SQ. METERS/GRAM. 